Multiple wafers are typically stored and transported together in batches by a wafer carrier throughout a semiconductor fabrication facility (“fab”) between the loadports of different wafer processing tools or equipment. Such tools generally perform various photolithography, etching, material/film deposition, curing, annealing, inspection, or other processes used in IC chip manufacturing. One such wafer carrier commonly used is a front opening unified pod (FOUP) which can hold a plurality of wafers ranging from 200 mm (8 inch) to larger 450 mm (18 inch) sizes. Typically, each wafer carrier holds on the order of approximately 25 wafers. The individual wafers are stacked vertically in the FOUP and stored in a wafer support frame having multiple separate wafer shelves or slots.
Wafer processing tools or equipment have motorized robots that are automatically controlled and operated by a programmable computer or processor to retrieve a wafer from the FOUP, load the wafer into the fabrication tool or other equipment, and then return the wafer to the FOUP. These robots have an adjustable motor controller operable to guide movement of a feed arm associated with the robot which are configured with a hand for grasping a wafer. The accuracy with which the robot can physically locate each individual wafer in its respective slot in the wafer carrier for retrieval and re-insertion is important for avoiding physical damage to the wafer such as scratching or chipping upon contact with surfaces in the wafer carrier or other objects.
Before routine operation of the tool or equipment during wafer processing, an initial tool setup procedure is typically performed to “teach” the robot movements in spatial relationship to the location of the slots and wafers to be positioned therein in the FOUP. The setup procedure is therefore used to fine tune and make adjustments to the linear travel, angular orientation, rotational movement, and positioning of the robotic feed arm with respect to the FOUP and anticipated location of the wafer in each slot during normal tool operation. Heretofore, such initial adjustments have sometimes relied on subjective methods based on the experience and expertise of the technicians (i.e. “gut feeling”) that the robotic arm positioning adjustments made will result in accurate wafer picks and returns to the FOUP slots. This setup procedure and approach is generally time consuming, cannot be easily replicated, and not sufficiently accurate in all cases to avoid costly wafer damage.
All drawings are schematic and are not drawn to scale.